package com.fynu.text;

import java.util.Random;

public class Main {
    public static void main(String[] args) {
        char[] arr = new char[52];
        int j = 0;
        for (int i = 65; i < 91; i++) {
            arr[j] = (char)(i);
            j++;
        }
        for (int i = 97; i < 123; i++) {
            arr[j] = (char)(i);
            j++;
        }
        Random rd = new Random();
        for (int i = 0; i < 4; i++) {
            int number = rd.nextInt(52);
            System.out.print(arr[number]);
        }
    }
}
